The overall objective of this proposal is to define the physiological and biochemcial bases for the release of lysosomal protein into bile. We are exploring the hypothesis that exocytosis of lysosomal contents into biliary canaliculi is a major excretory route for hepatocyte lysosomes. To date, we have: 1) Established valid assay conditions for three lysosomal hydrolases (beta-galactosidase, N-acetyl-beta-glucosaminidase, and beta-glucuronidase), two plasma membrane enzymes (5'-nucleotidase and alkaline phosphodiesterase 1) and a single soluble enzyme (LDH) in rat bile and liver; 2) Demonstrated that coordinate secretion of these three lysosomal hydrolases into rat bile occurs to a considerably greater extent than enzymes known to be associated with mitochondria, endoplasmic reticulum and cell sap; 3) Demonstrated in rats a dissociation of bile flow, biliary bile acid output, and biliary total protein output, from biliary lysosomal enzyme secretion under both non-cholestatic and cholestatic conditions; and 4) Demonstrated in hamsters that a non-cholestatic dose of ethynylestradiol causes an increase in hepatic lysosomal enzyme activity, an effect blocked by the anti-estrogen clomiphene.